Lecture 5: Cranial Nerves

Question 1

List the Olfactory nerves function

Answer 1

• Special sensory
• cell bodies in nasal mucosa
• olfactory nerve fibres synapse with mitral cells in olfactory bulb
• post-synaptic axons form the olfactory tract.
• only cranial nerve to enter the cerebrum directly

Question 2

List the function of cranial nerve 2

Answer 2

Cranial nerve 2 (optic) is actually an extension of the forebrain

• special sensory
• vision from retina
• cell bodies in retina
• terminate in lateral geniculate bodies of the thalamus
• post-synaptic axons to visual cortex in occipital lobe.

Question 3

Cranial nerve 3 function

Answer 3

CN 3: oculomotor
Origin and course: extend from ventral mid brain, pass through SOF to eye.
Function:
-somatic motor fibres to 4 of 6 extrinsic eye muscles, inferior oblique, and superior, medial and inferior rectus muscles.
Parasympathetic motor fibres to sphincter papillae (causes pupil to constrict)

• chief motor nerve to ocular and extra ocular muscles
• the oculomotor nerve originates from two nuclei in the medial aspect of the superior colliculus (midbrain)

Question 4

Cranial nerve 4
Origin and function
Does it carry parasympathetic fibres or sympathetic

Answer 4

Trochlear
Origin and course: Fibres emerge from dorsal midbrain and enter orbit through superior orbital fissure
Function: motor nerves; supply somatic motor fibres to and carry proprioceptor fibres from) the superior oblique

Question 5

Cranial nerve 5

Answer 5

Trigeminal, has 3 divisions. V1, V2, V3
V1 (ophthalmic):
Origin and course: fibres run from face to pons via SOF
Function: conveys sensory impulses from skin of anterior scalp, upper eyelids, and nose, and cornea and lacrimal gland.
V2: maxillary division
Origin and course: fibres run from face to pons via foramen rotundum
Function: conveys sensory impulses from palate, upper teeth, skin of cheek, lower eyelid
V3: mandibular division
Origin and course: fibres pass through skull via foramen ovale
Function : conveys sensory impulses from anterior tongue, lower teeth, temporal region of scalp.
Motor fibres to muscles of mastication

Question 6

Cranial nerve 6

Answer 6

Abducens
Origin and course: fibres leave inferior pons and enter orbit via superior orbital fissure to run to eye.
Function: motor to lateral rectus muscle

Question 7

Cranial nerve 7

Answer 7

Facial nerve
Origin and course: fibres from pons enter via internal acoustic meatus and run through the ear cavity before coming out of style mastoid foramina, them goes to lateral aspects of the face.
Function: convey motor to face. Has 5 major branches. Temporal, zygomatic, buccal, mandibular and cervical.
Also transmit proprioceptor muscles from same muscle to pons.
-transmit parasympathetic motor impulses to lacrimal (tears), nasal and palatine glands
-conveys sensory from taste buds of anterior 2/3 of tongue

Question 8

Cranial nerve 8

Answer 8

Vestibulocochlear nerves
Origin and course: fibres arise from hearing and equilibrium systems pass through internal acoustic meatus to enter brain at pons, medulla boarder.
Function: sensory

Question 9

Cranial nerve 9:

Answer 9

Glossopharyngeal nerves
Origin and course: fibres come from medulla and leave skull via jugular foramen.
Function: both
-Motor to tongue and pharynx
-sympathetic motor to parotid salivary glands
Sensory:
-taste and touch from pharynx and posterior tongue form chemoreceptors

Question 10

Cranial nerve 10:

Answer 10

Vagus nerve:
Origin and course:
-only CN to extend beyond head and neck
-fibres emerge from medulla pass through skull via jugular foramen, and extend to thorax and abdomen.

Function:

• mixed nerves. Nearly all parasympathetic efferent
• parasympathetic motor supply heart, lungs, abdominal viscera, and help regulate heart rate, breathing and digestive activity.

-sensory impulses from thoracic and abdominal viscera, and the taste buds of posterior tongue and pharynx

Question 11

Cranial nerve 11

Answer 11

Accessory nerve
Origin and course:
-emerge from ventral rootless from spinal cord, and enter skull via foramen magnum.
-accessory nerve exits the skull via jugular foramen

Function:
Motor fibres to trapezius and sternocleidomastoid

Question 12

Memorise diagram on slide 5 and 6

Answer 12

Do it!

Question 13

Cranial nerve 12

Answer 13

Hypoglossal
Origin and course: fibres arise from medulla and exit from skull via hypoglossal canal to travel to tongue.
Function: mixed nerves, primarily motor function.
-motor to extrinsic and intrinsic muscles of tongue.
-allows for tongue movement that contributes to swallowing and speech.